"I think ISIS can do terrible things," McCain said. "But it's the Russians who tried to destroy the fundamental of democracy and that is to change the outcome of an American election."

McCain said while he has seen "no evidence" that Moscow successfully influenced the American presidential election, he noted that the Russians "tried, and are still trying."

"They're still trying to change elections,. They just tried to affect the outcome of the French election," he added.

McCain slammed the Trump administration's response to Russia's attempts to influence the U.S. election, and is calling for sanctions.

"We have done nothing since the election last November to respond to Vladimir Putin's attempt to change the outcome of our elections. So, way to go Vladimir. We haven't responded at all," McCain said.

The Republican senator also addressed recent reports that President Trump's senior adviser and son-in-law Jared Kushner attempted to set up a secret line of communications with Russia before Trump took office.

"I know some administration officials are saying this is standard procedure. I don't think it's standard procedure prior to the inauguration of the president of the United States by someone who is not in an appointed position," he said. "This is becoming more and more bizarre. In fact, you can't make it up."

McCain also said that Trump's unpredictability makes him "nervous from time to time."

"I do believe that the President has great confidence in this national security team. I do believe most of the time that he accepts their advice and counsel," he said. "Can I tell you that he does all the time? No. Does it bother me? Yes, it bothers me."